CN1897331B - Positive electrode for lithium secondary battery, and lithium secondary battery using the same - Google Patents

Positive electrode for lithium secondary battery, and lithium secondary battery using the same Download PDF

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Publication number
CN1897331B
CN1897331B CN200610105690.2A CN200610105690A CN1897331B CN 1897331 B CN1897331 B CN 1897331B CN 200610105690 A CN200610105690 A CN 200610105690A CN 1897331 B CN1897331 B CN 1897331B
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lithium
positive electrode
temperature
containing compound
secondary battery
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CN1897331A (en
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武泽秀治
西野肇
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/40—Alloys based on alkali metals
    • H—ELECTRICITY
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M4/364—Composites as mixtures
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
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    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

A positive electrode for use in a lithium secondary battery comprises a positive electrode current collector, and a positive electrode film which is carried on the positive electrode current collector and includes a plurality of mixture layers. The positive electrode film contains, as a positive electrode active material, two or more kinds of lithium-containing compounds having exothermic initiation temperatures different from each other. At least one kind of the two or more kinds of lithium-containing compounds has the exothermic initiation temperature of 300 DEG C or higher. A first mixture layer of the plural mixture layers closest to the positive electrode current collector contains at least one kind of the lithium-containing compound having the exothermic initiation temperature of 300 DEG C or higher. Thereout, it can restrain the overheating of the battery availably in the nailing test, and can provide a positive electrode for use in a lithium secondary battery with a high capability.

Description

Positive electrode for lithium secondary battery and used this anodal lithium secondary battery
Technical field
The reliability that the present invention relates to test by pin prick test is good and be the positive electrode for lithium secondary battery of high power capacity and used this anodal lithium secondary battery.
Background technology
Lithium secondary battery is used as the working power of laptop or portable communication device etc.In recent years, along with the development of portability or wirelessization of electronic equipment, the requirement of high capacity or miniaturization and strengthens gradually.Be accompanied by this trend, by the improvement of electrode material or the improvement of change or battery structure etc., lithium secondary battery carries out high capacity just gradually.On the other hand, owing to being accompanied by high capacity, energy density also increases, and therefore also becomes high for the requirement that improves the reliability while discharging compared with macro-energy in internal short-circuit test etc.Therefore, strong request can take into account high reliability in this test and the lithium secondary battery of high power capacity.
One of test of reliability during as detection internal short-circuit, oriented battery thrusts the internal short-circuit test (being designated hereinafter simply as " pin prick test ") of nail.The lithium secondary battery that energy density is high, if in pin prick test because internal short-circuit makes anodally while starting thermal decomposition, can discharge compared with macro-energy, thermal runaway occurs and make battery overheated.Therefore, the lithium secondary battery in pin prick test overheated, is subject to the considerable influence of anodal thermal stability.
Anodal thermal stability depends on the thermal stability of the active material adopting in positive pole.Active material used in positive pole as lithium secondary battery, known have a LiCoO with bedded structure 2or LiNiO 2, there is the LiMn of spinelle structure 2o 4deng the composite oxides that contain lithium.These lithium-contained composite oxides, its electrochemical properties and thermal stability are different.
For example, LiNiO 2deng the reversible capacity of lithium nickel oxide be 180～200 (mAh/g), although capacity density is larger compared with other otide containing lighium thing, it is low that heating starts temperature, thermal stability is low.Therefore the lithium secondary battery, using it as positive active material has easily overheated tendency in pin prick test.
Therefore, in order to improve anodal thermal stability in maintaining high power capacity, propose following lithium secondary battery,, to suppress the emitting as object of oxygen when thermal decomposition, used LiNiO 2a part of middle Ni is replaced into the otide containing lighium thing of other elements as the lithium secondary battery of positive active material; Lithium nickel oxide and the otide containing lighium thing higher than its thermal stability are combined and form anodal lithium secondary battery using them as active material.
For example, the positive pole of the lithium secondary battery that JP 2003-036838 communique (being designated hereinafter simply as " patent documentation 1 ") proposes, there is 2 layers or more multi-layered mixture layer comprising as the otide containing lighium thing of positive active material on the surface of current collection base material, use heating to start the high positive active material of temperature on the top layer of mixture layer.The prior art can prevent that following situation from occurring: in pin prick test, and when running through negative pole and becoming the nail of negative pole current potential and the moment that positive pole contacts, its anodal most surface stream super-high-current, generation Joule heat, and because this heat makes the anodal thermal decomposition that occurs.
The object of pin prick test is: have a mind to cause the internal short-circuit occurring because of foreign matter etc., investigate battery have or not overheated.Therefore, pin prick test preferably in imagination under the internal short-circuit condition of harsh as far as possible environment for use, carry out.For example, in pin prick test, can internal short-circuit occur more effectively compared with when fast with speed in the time that the speed of acupuncture is slow, electric current concentrates on short position, and therefore battery easily becomes superheat state.Especially carried out the lithium secondary battery of high capacity, carried out pin prick test under this internal short-circuit condition, it is overheated to be required not occur.
But, the inventor studies in great detail by lithium secondary battery, find: though for example adopt in patent documentation 1 disclosed positive electrode for lithium secondary battery might as well, under harsh like this internal short-circuit condition, carry out pin prick test, just can not significantly suppress the overheated of lithium secondary battery.
Summary of the invention
The present invention makes in light of this situation, its object is: a kind of positive electrode for lithium secondary battery is provided, even in the pin prick test that has made in imagination to carry out under the internal short-circuit condition of harsh environment for use, also can conscientiously suppress the overheated of lithium secondary battery; And provide and use its lithium secondary battery that reliability is good and capacity is high.
For reaching this object, the positive electrode for lithium secondary battery that one aspect of the present invention provides, comprises current collection base material and on described current collection base material, has the anodal film of multiple mixture layers; Wherein, described anodal film, contains the lithium-containing compound that starts different two or more of temperature as the heating of positive active material; In described two or more lithium-containing compound, at least a kind of lithium-containing compound has 300 ℃ of above heatings and starts temperature; The 1st mixture layer nearest with described current collection base material, contains at least a kind of described heating and starts the lithium-containing compound of temperature more than 300 ℃.
About the Heating mechanism being caused by internal short-circuit in the pin prick test for example, carrying out with the acupuncture speed of low speed, about 5mm/s, find according to the inventor's research, the position that the maximum of the heat energy being produced by internal short-circuit discharges, not the top layer of running through negative pole and becoming anode mixture that the nail of negative pole current potential is initial contacted, but anodal current collection base material or anodal current collection base material and the interface portion of anodal film.
That is to say, due to internal short-circuit, be mainly that this heat makes lithium secondary battery overheated because the conducting of anodal current collection base material and negative pole current collection base material produces Joule heat.The heat of Joule heat is deferred to Joule law, square being directly proportional of the electric current (being designated hereinafter simply as " short circuit current ") during to short circuit.Based on this relation, can think that short circuit current just easily flows through in the time that the resistance (being designated hereinafter simply as " short-circuit resistance ") at internal short-circuit position diminishes, the Joule heat producing uprises.The resistivity of the aluminium foil here, using usually used as anodal current collection base material is 2.75 × 10 -6Ω cm, (is about 10～10 with the resistivity of common anode mixture layer 4Ω cm) compare much smaller.
Therefore can think, nail, in the time contacting with the aluminium foil of anodal current collection base material, flows through larger short circuit current than the skin section of the anode mixture layer large with resistivity while contact, thereby produces higher Joule heat.
An above-mentioned aspect of the present invention is made based on this opinion.
That is to say, by making anodal film have multiple mixture layers, and make with pin prick test in produce because of internal short-circuit in the 1st nearest mixture layer of the current collection base material of very high Joule heat, contain at least a kind of heating and start the lithium-containing compound of temperature more than 300 ℃, conscientiously suppress the anodal heating being caused by internal short-circuit, anodal thermal runaway is limited in to Min..In addition, because anodal film of the present invention can contain " other lithium-containing compounds except heating starts the lithium-containing compound of temperature more than 300 ℃ ", can contain " although heating starts lower but other lithium-containing compounds that capacity density is large of temperature ", therefore can make anodal entirety realize high power capacity.Consequently, can conscientiously suppress battery in pin prick test overheated, and the positive electrode for lithium secondary battery of high power capacity can be provided.
The positive electrode for lithium secondary battery that another aspect of the present invention provides, comprises current collection base material and the anodal film on described current collection base material; Wherein, described anodal film, contains the lithium-containing compound that starts different two or more of temperature as the heating of positive active material; In described two or more lithium-containing compound, at least a kind of lithium-containing compound has 300 ℃ of above heatings and starts temperature; On the top layer of described anodal film, to the thickness direction of current collection base material, described heating starts the content of the lithium-containing compound of temperature more than 300 ℃, increases towards current collection base material side from top layer side.
In addition, the invention provides a kind of lithium secondary battery, possess above-mentioned positive electrode for lithium secondary battery, negative pole and nonaqueous electrolyte.
Object of the present invention, feature, mode and advantage, can be more clear by following detailed description and accompanying drawing.
Accompanying drawing explanation
Fig. 1 is the schematic cross sectional view that represents an example of the positive electrode for lithium secondary battery of embodiments of the present invention 1.
Fig. 2 is the schematic cross sectional view that represents an example of the positive electrode for lithium secondary battery of embodiments of the present invention 2.
Embodiment
Below embodiments of the present invention are elaborated.
< execution mode 1>
The positive electrode for lithium secondary battery of present embodiment is the positive electrode for lithium secondary battery that has possessed current collection base material, has the anodal film of multiple mixture layers on described current collection base material; Anodal film, contain as positive active material, heating starts the lithium-containing compound of different two or more of temperature; In the lithium-containing compound of two or more, at least a kind of lithium-containing compound has 300 ℃ of above heatings and starts temperature; The 1st mixture layer nearest with current collection base material, contains at least a kind of described heating and starts the lithium-containing compound of temperature more than 300 ℃.
The positive electrode for lithium secondary battery of present embodiment is described with accompanying drawing.
Fig. 1 is the schematic cross sectional view that represents an example of the positive electrode for lithium secondary battery of present embodiment.
The positive electrode for lithium secondary battery of Fig. 1 is formed with anodal film 2 on current collection base material 1, anodal film 2 is by with nearest the 1st mixture layer 3 of current collection base material 1 and form these 2 layers of mixture layer 4 of its outer layer side (in specification, sometimes also referred to as " top layer side ") and form.Although it is the situation of 1 layer that Fig. 1 has represented the mixture layer of the outer layer side that forms the 1st mixture layer, the mixture layer that forms the outer layer side of the 1st mixture layer also can form 2 layers or more multi-layered.In the anodal film 2 being made up of 2 laminated doses of layers, contain heating start 2 kinds of different lithium-containing compounds of temperature as positive active material, a kind of lithium-containing compound in 2 kinds of lithium-containing compounds has 300 ℃ of above heatings and starts temperature.In addition, contain heating with nearest the 1st mixture layer 3 of current collection base material and start the lithium-containing compound 5 of temperature more than 300 ℃.Mixture layer 4 contains other lithium-containing compounds 6 in addition, i.e. heating and starts lower and other lithium-containing compounds that capacity density is large of temperature.The 1st mixture layer 3, except lithium-containing compound 5, can also contain other lithium-containing compounds 6.In addition, mixture layer 4, except other lithium-containing compounds 6, can also contain lithium-containing compound 5.
As long as the positive pole of aforesaid way, even in the time of pin prick test, with the nail of negative pole current potential arrives current collection base material 1 because internal short-circuit has produced high Joule heat, due to the 1st nearest mixture layer 3 of this current collection base material 1 in contained lithium-containing compound 5 there are 300 ℃ of above heatings and start temperature, therefore can suppress anodal thermal runaway, avoid the further overheated of battery.In addition, even if containing heating compared with lithium-containing compound contained in the 1st mixture layer 3, mixture layer 4 starts other lower lithium-containing compounds 6 of temperature, owing to having avoided contacting with the direct of current collection base material 1 by the 1st mixture layer 3 higher than current collection base material 1 resistivity, therefore do not worry causing thermal runaway.And, because the capacity density of other lithium-containing compounds 6 contained in mixture layer 4 is large, therefore can realize high power capacity.
In present embodiment, start the just passable of temperature with the contained lithium-containing compound of nearest the 1st mixture layer of current collection base material 1 as long as thering are 300 ℃ of above heatings.If divided generally starting temperature according to its heating as the lithium-containing compound of positive active material, take the scope of approximately 250～300 ℃ as boundary, can roughly be divided into the lithium-containing compound that there are the i.e. 300 ℃ of above heatings of its high temperature side and start the lithium-containing compound of temperature and there are the i.e. 250 ℃ of following heatings of its low temperature side to start temperature.According to the inventor's research, start the 1st mixture layer of the lithium-containing compound of temperature more than 300 ℃ as long as containing heating, in the pin prick test of low speed, even at the high Joule heat of generation of interfaces of anodal current collection base material and anodal current collection base material and the 1st mixture layer, but because the heating of the 1st mixture layer is suppressed, therefore can prevent the overheated of battery.
Here, the heating of the lithium-containing compound of present embodiment starts temperature, for example, can measure as described below.In the time measuring from the lithium-containing compound obtaining by given manufacture method, in described lithium-containing compound, add conductive agent, binding agent, be made into the electrode of sheet, in the evaluation electricity consumption groove that sets it as the work utmost point, charge to after given voltage, positive active material is sampled, measure with differential scanning calorimetry (DSC).In addition, in the time measuring from the lithium secondary battery being made into, will charge to the lithium secondary battery of given voltage decompose and reclaim positive active material, measure with DSC.Condition determination is that sample is heated up with the programming rate of 10 ℃/min, and the Temperature Setting that the curve of the DSC of gained is started to rise from baseline is heating beginning temperature.In general, heating starts the stable more difficult pyrolysis that causes positive active material of lithium-containing compound of temperature crystal structure high and in the time of high temperature, and therefore heating beginning temperature is to evaluate the leading indicator of the thermal stability of positive active material.
In present embodiment, the heating contained with nearest the 1st mixture layer of current collection base material starts the lithium-containing compound of temperature more than 300 ℃, can be a kind, can be also two or more.When using a kind time, start among the lithium-containing compound of temperature 300 ℃ or more from heating, preferably there is higher for example 400 ℃ of heatings above and start the lithium-containing compound of temperature.In the time using two or more heatings to start the lithium-containing compound of temperature more than 300 ℃, the viewpoint of the positive pole heating being caused by internal short-circuit from practical inhibition, preferably increases the content that for example has 400 ℃ of above heatings and start the lithium-containing compound of temperature.
In the 1st mixture layer,, except heating starts the lithium-containing compound of temperature more than 300 ℃, can also contain and start other lithium-containing compounds that temperature is lower except the heating it as positive active material.In this case, the viewpoint of generating heat from the positive pole that suppresses to be caused by internal short-circuit, the content that preferably heating starts the lithium-containing compound of temperature more than 300 ℃ is more than the content except other lithium-containing compounds it.In addition, in the middle of the lithium-containing compound in the 1st mixture layer, the heating more preferably containing more than 80 quality % starts the lithium-containing compound of temperature more than 300 ℃.More preferably more than 90 quality %, most preferably be 100 quality %.
In present embodiment, form 1 layer or the mixture layer of multilayer of the outer layer side of the 1st mixture layer, although other lithium-containing compounds, the i.e. heating that contain except heating starts the lithium-containing compound of temperature more than 300 ℃ start temperature lower than 300 ℃ of other lithium-containing compounds that capacity density is large.Forming contained described other lithium-containing compounds in the mixture layer of 1 layer of outer layer side of the 1st mixture layer or multilayer, can be a kind, can be also two or more.For example, be 1 layer if form the mixture layer of the outer layer side of the 1st mixture layer, in this layer, both can contain a kind, also can contain described other lithium-containing compounds of two or more.In addition, be 2 layers or more multi-layered if form the mixture layer of outer layer side of the 1st mixture layer, also can in its each layer, contain respectively one or more and there is different heatings and start described other lithium-containing compounds of temperature.
In the mixture layer that forms 1 layer of outer layer side of the 1st mixture layer or multilayer, also can contain heating and starting the lithium-containing compound of temperature more than 300 ℃.In this case, from expecting the viewpoint of high capacity, although above-mentioned heating starts the content of temperature lower than other large lithium-containing compounds of 300 ℃ of capacity densities, preferably start the content of the lithium-containing compound of temperature more than 300 ℃ more than heating.More than described other lithium-containing compounds more preferably contain 80 quality %, more than further preferably containing 90 quality %.
In present embodiment, in the top layer of the anodal film being formed by multiple mixture layers, also can in fact only contain heating and starting the lithium-containing compound of temperature more than 300 ℃.For example, in pin prick test at a high speed, even produced Joule heat at this anodal most surface stream super-high-current with the anodal moment contacting at the nail that has run through negative pole, also can prevent the anodal thermal decomposition being caused by this heat.
In present embodiment, owing to starting the lithium-containing compound of temperature more than 300 ℃ by contain heating in the 1st mixture layer, can effectively suppress the generation of the high Joule heat being caused by internal short-circuit in pin prick test, therefore also can be by the reduced thickness of the 1st mixture layer in multiple mixture layers on current collection base material.And, by the thickness of attenuate the 1st mixture layer, form the relative thickening of thickness of the mixture layer of 1 layer of its outer layer side or multilayer, also contain to high concentration therein other lithium-containing compounds that capacity density is large.
The average thickness of the 1st mixture layer can be thinned to the scope of 0.5～20 μ m at the one side of current collection base material, be preferably set to 2～15 μ m, is more preferably set as 5～10 μ m.In addition, the ratio of the average thickness of the average thickness of the 1st mixture layer and its skin (1 layer or multilayer) is preferably in the scope of 0.5: 100～20: 100, more preferably in the scope of 5: 100～18: 100.
In present embodiment, start the lithium-containing compound of temperature more than 300 ℃ as heating, a kind of being selected from lithium manganese type oxide, lithium nickel cobalt manganese type oxide and olivine-type lithium phosphate compounds can be illustrated as to preferred lithium-containing compound.These lithium-containing compounds not only generate heat, and to start temperature high, and has the crystal structure that is difficult for thermal decomposition, is therefore preferred.
In present embodiment, these lithium-containing compounds, in the pin prick test of low speed, all demonstrate and have the excellent results that has substantially suppressed the cell voltage reduction being caused by short circuit.Based on this effect, can know the positive electrode for lithium secondary battery that has used these lithium-containing compounds, can conscientiously suppress the overheated of lithium secondary battery in pin prick test.
And, in the time having produced internal short-circuit in the pin prick test at low speed, although reduce because the generation of Joule heat makes cell voltage, above-mentioned lithium-containing compound can not only suppress the reduction of cell voltage, but also has the character of the voltage that minimum voltage can return to than short circuit time is higher.The potential difference of the voltage when minimum voltage therefore, also can utilize short circuit time and recovery is controlled and is discharged and recharged.
As lithium manganese type oxide, preferably use by LiMn 2o 4the lithium manganese oxide of the spinelle structure type representing.Start temperature high (being measured as 320 ℃ according to said determination method) because this lithium manganese oxide not only generates heat, and heat decomposition temperature is high, oxygen discharging amount when decomposition is also few, and therefore thermal stability is high.In addition, in order to improve the cycle characteristics of lithium manganese type oxide, the part that also can use Mn by other element substitutions such as Cr, Fe, Mg, Al lithium manganese type oxide.
Lithium-nickel-manganese-cobalt type oxide is the material that also contains nickel and cobalt in the composition of lithium manganese type oxide.As lithium-nickel-manganese-cobalt type oxide, preferably use by chemical formula Li ani 1-(b+c)mn bco co 2the lithium-nickel-manganese-cobalt oxide that (wherein, 1≤a≤1.2,0.1≤b≤0.5,0.1≤c≤0.5) represents.The lithium-nickel-manganese-cobalt oxide of this composition not only has stable characteristic, and can obtain at an easy rate.Here, a value is preferably 1≤a≤1.2.When a when above, due to the lithium salts abundance using as raw material, therefore can suppress the existence of the impurity of the electrochemistry such as nickel oxide, cobalt oxide inertia 1 more conscientiously, be difficult for bringing out volume lowering.In addition, in the time that a value is below 1.2, because the lithium salts using as raw material can not exist surplus, therefore can suppresses more effectively lithium compound and exist as impurity, be difficult for equally bringing out volume lowering.Composition when described a value is uncharged.In addition, b value is preferably 0.1≤b≤0.5.This be because, when b when above, can obtain the effect that improves thermal stability 0.1 more effectively, if b, below 0.5, is difficult for occurring volume lowering.In addition, c value is preferably 0.1≤c≤0.5.This is because when c is 0.1 when above, the further stabilisation of crystal structure, is difficult for producing the problem on cycle characteristics, if c, below 0.5, is difficult for occurring volume lowering.For example, according to described assay method, by LiNi 1/3mn 1/3co 1/3o 2it is 305 ℃ that the heating of the lithium-nickel-manganese-cobalt oxide representing starts temperature.
As olivine-type lithium phosphate compounds, be preferably by LiMePO 4the olivine-type lithium phosphate compound that (wherein, Me is at least a kind that is selected from Co, Ni, Fe and Mn) represents.Olivine-type lithium phosphate compound not only has the crystal structure that is difficult for thermal decomposition, and has high heating and start temperature.For example, LiFePO 4there is high heating and start temperature, according to described assay method, start even also do not observe above heating at 400 ℃.This phenomenon is considered to owing to forming close-packed hexagonal structure and Li and Fe with oxygen atom and account for octahedral center when, P accounts for that olivine-type crystal structure that tetrahedral center forms causes.
In present embodiment, as start other lithium-containing compounds the lithium-containing compound of temperature more than 300 ℃ except heating, at least a kind of being selected from lithium-cobalt oxide and lithium nickel type oxide can be enumerated as to preferred lithium-containing compound.
As lithium-cobalt oxide, preferably use LiCoO 2or by Li aco 1-(b+c)mg bm co 2the lithium-cobalt oxide that (wherein, 1≤a≤1.05,0.005≤b≤0.10,0.005≤c≤0.10, M is at least a kind that is selected from Al, Sr and Ca) represents.Here, when a value that represents lithium amount is 1 when above, due to the lithium salts abundance as raw material use, therefore the impurity of the electrochemistry inertia such as cobalt oxide exist suppressedly, be difficult for bringing out volume lowering.In the time that a value is below 1.05, because the lithium salts using as raw material can not exist surplus, therefore can suppress lithium compound remaining as impurity, be difficult for equally bringing out volume lowering.Composition when described a value is uncharged.In addition, in the time of the scope of b value in 0.005≤b≤0.10, as the effect of Mg, can improve the stability of crystal structure in the time of high temperature, further improve thermal stability.And, owing to can alleviating by being accompanied by the break reduction of (particle cracking) caused discharge capacity of lattice deformability (latticedistortion), structure destruction (structure breakage) and particle that the dilation that discharges and recharges causes, therefore can further improve cycle characteristics.In addition, when c value is 0.005 when above, crystal structure is stable, and thermal stability improves.In the time that c value is below 0.10, be difficult for producing volume lowering.For example, according to described assay method, LiCoO 2heating start temperature and by LiCo 0.98mg 0.02o 2the heating of the lithium-cobalt oxide representing starts temperature and is respectively 202 ℃ and 208 ℃.
As lithium nickel type oxide, preferably use by Li ani 1-(b+c)co bm co 2the lithium nickel type oxide that (wherein, 1≤a≤1.05,0.1≤b≤0.35,0.005≤c≤0.30, M is at least a kind that is selected from Al, Sr and Ca) represents.By being set as this composition, can improve as LiNiO 2the physical property of the active material of base, is accompanied by that the crystal structure that discharges and recharges changes greatly and invertibity is poor although capacity density is high.This lithium nickel oxide compares LiCoO 2the active material cheapness of base, special is useful as the positive electrode active material material for large-sized battery.Here, when a value is 1 when above, due to the lithium salts abundance using as raw material, therefore the impurity of the electrochemistry such as nickel oxide, cobalt oxide inertia exist suppressedly, be difficult for bringing out volume lowering.In the time that a value is below 1.05, because the lithium salts using as raw material can not exist surplus, therefore can suppress lithium compound remaining as impurity, be difficult for equally bringing out volume lowering.Composition when described a value is uncharged.In addition, b value is preferably 0.10≤b≤0.35.When b when above, can obtain described effect 0.1 more effectively, if b is below 0.35, be difficult for producing volume lowering.In addition, when c value is 0.005 when above, thermal stability improves, and in the time that c value is below 0.3, is difficult for generation volume lowering.As lithium nickel type oxide, for example, by LiNi 0.82co 0.15al 0.03o 2the heating of the lithium nickel type oxide representing starts temperature, is measured as 215 ℃ according to described assay method.
The positive electrode for lithium secondary battery of present embodiment, for example, can make with the following method.
Start the lithium-containing compound of temperature more than 300 ℃ for example in olivine-type lithium phosphate compounds to a certain amount of heating, add anodal binding agent and conductive agent etc. and stir, make anode mixture cream and stick with paste.In addition, similarly making the anode mixture cream that contains for example lithium-cobalt oxide of other lithium-containing compounds except heating starts the lithium-containing compound of temperature more than 300 ℃ sticks with paste.The anode mixture cream that for example, contains olivine-type lithium phosphate compounds at the surface-coated of current collection base material (aluminium foil) is stuck with paste and is dried, and forms the 1st mixture layer.The anode mixture cream that coating contains lithium-cobalt oxide is thereon stuck with paste and is dried.After dried coating film, make it to roll, can obtain for example having by the anode mixture layer of 2 layers and the positive plate of the film forming.
As anodal current collection base material, as long as not causing the electric conductor of chemical change under the charge and discharge potential of the positive electrode used, be just not particularly limited.The material that is generally used as current collection base material is aluminium (Al).In addition, except titanium (Ti), stainless steel (below sometimes referred to as " SUS "), carbon, electroconductive resin etc., can also use the material that has carried out carbon or Ti processing on the surface of Al or SUS.Particularly from the viewpoint of cost, processability or stability, preferred Al or Al alloy.Also the surface oxidation of these materials can be used.In addition, can also utilize surface treatment to make current collection substrate surface with concavo-convex.In addition, also can use on the resin flakes such as PET Al or Ti are made to film and the material of affix by methods such as evaporations.Shape except paillon foil, can also use film, laminar, netted, by formed body punching, lath body (lath sheet), porous body, foaming body, fiber group, nonwoven fabrics body etc.Although thickness is not particularly limited, be preferably 1～50 μ m.
The anodal film of present embodiment can be made with the following method, be that binding agent, the conductive agent mixing in solvent (mixing) of above-mentioned positive active material and use are as required made it to disperse, like this, the mixture cream that obtains is stuck with paste and is coated on anodal current collection base material, roll after dry and make.In addition, also can make by the vacuum film formation technique of sputter etc.As required, also can be by these Combination of Methods.
The binding agent that mixture cream adds in sticking with paste can be any in thermoplastic resin, thermosetting resin.For example, can use with the common resin being used headed by polyethylene, polypropylene, polytetrafluoroethylene (PTFE), Kynoar (PVDF), butadiene-styrene rubber (SBR).These materials both can use separately, also can be used as mixture and used.
The conductive agent adding in sticking with paste as mixture cream, can use conductive material.For example, can enumerate the graphite-likes such as native graphite (flaky graphite etc.), Delanium, expanded graphite; The carbon black classes such as acetylene black, section's qin carbon black; The conducting fibre such as carbon fiber, metallic fiber class; The organic conductive materials such as the metal dust such as copper, nickel class and polyphenyl derivative.They both can use separately, also can use by multiple combination.In these conductive agents, the carbon black class such as acetylene black, section's qin carbon black that preferably particulate and conductivity are high.The addition of conductive agent only otherwise damage effect of the present invention, is just not particularly limited.
The solvent of sticking with paste for making mixture cream, for example, can use the organic solvents such as METHYLPYRROLIDONE (NMP), but be not limited thereto.
For by positive active material and the conductive agent, the binding agent that use as required mixing in solvent, disperse and the method for making pasty state mixture is not particularly limited.For example, can use planetary-type mixer, homogeneous mixer, leaf formula mixer, kneader, homogenizer etc.They can be used singly or in combination.In addition, in the time of the mixing dispersion of described mixture cream paste, also can add as required thickener, various dispersant, surfactant, stabilizer etc.
Be not particularly limited for the coating on current collection base material, dry and calendering.Coating can be passed through as above by the mixture of mixing dispersed pasty state, with slit die coating machine such as, reversing roll-coater, lip coating machine (lip coater), blade coating machine, doctor knife coater, intaglio plate coating machine, dip coater etc., be coated with easily and make it coating.Dry preferably natural drying, but consider productivity, preferably dry at the temperature of 70 ℃～200 ℃.Calendering preferably utilizes roll press to be calendered to given thickness.
The lithium secondary battery of present embodiment can be made in the following manner,, make make the positive electrode for lithium secondary battery that obtains and negative pole as said method relatively and by its coiling or the electrode body that is laminated across barrier film, then this electrode body is enclosed in battery case together with nonaqueous electrolyte and make.
Be not particularly limited for negative pole.As negative electrode active material, for example, the known materials such as the carbon class materials such as graphite, the metal, alloy or the oxide that comprise silicon (Si), tin (Sn) etc., carbide, nitride material, salt can be used alone or in combination.Negative pole for example can be made in the following manner,, by negative electrode active material, as required use binding agent, conductive agent, thickener mixing in solvent, disperse and be prepared into cream stick with paste, this cream is stuck with paste to be coated on current collection base material made of copper make to reach given thickness, after dry, calendering, carry out cutting and make.
As nonaqueous electrolyte, can be not only liquid electrolyte, can be also the electrolyte of gel or solid.As liquid electrolyte, can use the material of the additive that has dissolved solute and add as required in nonaqueous solvents.For nonaqueous solvents, preferably use the carbonic esters such as ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, but be not limited to these.Nonaqueous solvents is preferably used in combination two or more.For solute, preferably use LiPF 6, LiBF 4deng lithium salts, but be not limited to these.As additive, for example, can use vinylene carbonate, cyclohexyl benzene etc.
As barrier film, although be not particularly limited, can use the micro-porous membrane being formed by the vistanex such as polyethylene, polypropylene.
The lithium secondary battery of present embodiment goes for the shape arbitrarily such as large-sized battery used in Coin shape, button type, sheet type, cascade type, cylinder type, platypelloid type, square, electric automobile etc.
< execution mode 2>
The positive electrode for lithium secondary battery of present embodiment is following positive pole, that is: be formed in the anodal film on current collection base material, contains heating and start the lithium-containing compound of different two or more of temperature as positive active material; At least a kind of lithium-containing compound in the lithium-containing compound of two or more has 300 ℃ of above heatings and starts temperature; Anodal film from top layer current collection base material thickness direction, described heating starts the content of the lithium-containing compound of temperature more than 300 ℃, increases towards described current collection base material side from described top layer side.
The positive electrode for lithium secondary battery of present embodiment is described with accompanying drawing.Because current collection base material, active material etc. are identical with execution mode 1, the part therefore repeating is omitted, and different parts is described.
Fig. 2 is the schematic cross sectional view that represents an example of the positive electrode for lithium secondary battery of present embodiment.
On current collection base material 1, be formed with anodal film 2, in anodal film 2, contain heating as positive active material and start a kind of lithium-containing compound 5 in different 2 kinds of lithium-containing compounds 5 and 6, the 2 kind of lithium-containing compound of temperature and there are 300 ℃ of above heatings and start temperature.And on the thickness direction from top layer side to current collection base material side of anodal film 2, heating starts the content of the lithium-containing compound 5 of temperature more than 300 ℃, increases towards described current collection base material side from described top layer side.
As long as the positive pole of described mode, even if in pin prick test, nail contacts with current collection base material 1 while making to have produced high Joule heat because of internal short-circuit, the positive pole nearest with current collection base material 1 is coated with membrane portions because the amount that contains the lithium-containing compound 5 of heating beginning temperature more than 300 ℃ is for maximum, therefore can suppress anodal thermal runaway, avoid the further overheated of battery.Meanwhile, anodal film on the thickness direction of top layer side, due to other lithium-containing compounds, i.e. the content that heating starts low and other lithium-containing compounds 6 that capacity density is large of temperature increases, and therefore can realize high power capacity.Consequently, can conscientiously suppress battery in pin prick test overheated, and the positive electrode for lithium secondary battery of high power capacity can be provided.
Starting towards the thickness direction of current collection base material side from top layer side of anodal film, there are 300 ℃ of above heatings and start the lithium-containing compound of temperature, both can interimly increase, also can increase continuously.
Consider from the viewpoint that suppresses anodal thermal runaway, in anodal film, contained heating starts in the middle of the lithium-containing compound of different two or more of temperature, heating starts the containing ratio of the lithium-containing compound of temperature more than 300 ℃, being coated with in membrane portions with the nearest positive pole of current collection base material, more than being preferably 60 quality %, more preferably more than 80 quality %, more than being particularly preferably 90 quality %, most preferably be 100 quality %.In addition, consider from the viewpoint that improves anodal capacity density, in the middle of described two or more lithium-containing compound, the containing ratio of other lithium-containing compounds except heating starts the lithium-containing compound of temperature more than 300 ℃, with the top layer side part of current collection base material anodal film farthest in, more than being preferably 60 quality %, more preferably more than 80 quality %, more than being particularly preferably 90 quality %.
The positive electrode for lithium secondary battery of present embodiment, it is the lithium-containing compound that anodal film has heating and start different two or more of temperature, on the top layer of anodal film to the thickness direction of current collection base material, heating starts the content of the lithium-containing compound of temperature more than 300 ℃, increase from top layer side towards current collection base material side, the positive pole that contains this anodal film for example can be made with the following method.
As positive active material, by heating start the lithium-containing compound of temperature more than 300 ℃ for example olivine-type lithium phosphate compounds, except for example lithium-cobalt oxide of other lithium-containing compounds it, with certain total amount but change blending ratio mix, in the mixture obtaining, add respectively anodal binding agent and conductive agent etc. and stir, be made into anode mixture cream and stick with paste.The highest anode mixture cream of blending ratio at the surface-coated olivine-type lithium phosphate compounds of current collection base material (aluminium foil) is stuck with paste and is dried; The lower anode mixture cream of blending ratio that is coated with olivine-type lithium phosphate compounds is thereon stuck with paste and is dried.Then the minimum anode mixture cream of blending ratio that is coated with olivine-type lithium phosphate compounds is thereon stuck with paste, and the anode mixture cream that blending ratio of lithium-cobalt oxide is the highest is stuck with paste, and dry.Again the film of gained is rolled, can obtain the positive plate for example with following anodal film, the starting towards the thickness direction of current collection base material side from top layer side of described anodal film, the content of olivine-type lithium phosphate compounds periodically increases.
In addition, in above-mentioned anodal manufacture method, also can use following method, be coated with anode mixture cream and stick with paste, before dry, other anode mixture cream of coating are stuck with paste.For example, in sticking with paste to the highest anode mixture cream of the blending ratio of a certain amount of olivine-type lithium phosphate compounds, within the given time, the minimum anode mixture cream of the blending ratio of olivine-type lithium phosphate compounds stirring while successively marginally add same amount is stuck with paste, by the blending ratio obtaining in the process of interpolation gradually different anode mixture cream stick with paste coating successively, be dried thereafter.Again the film obtaining with said method is rolled, can obtain the positive plate with following anodal film, the starting towards the thickness direction of current collection base material side from top layer side of described anodal film, the content of olivine-type lithium phosphate compounds increases continuously.
The positive electrode for lithium secondary battery of the present embodiment obtaining by said method and execution mode 1 are faced to negative pole across barrier film in an identical manner, make its coiling or stacked electrode body, again this electrode body is enclosed in battery case together with nonaqueous electrolyte, can make lithium secondary battery of the present invention.
Although above present embodiment is had been described in detail, but described explanation is the illustration in whole modes, the present invention is not limited to them.Be understandable that, without departing from the scope of the invention, it is contemplated that out the countless variation that are not exemplified.
That below represent is the relevant embodiment of the present invention, but the present invention is not limited to these embodiment.In addition, in specification " more than " and " below " all comprise given figure, for example, " more than X " refers to " equal X or be greater than X ", " X following " refers to " equal X or be less than X ", " exceeding ", " exceeding ", " less than " and " deficiency " neither comprise given figure.
Embodiment
(i) preparation of positive active material
Utilize respectively following method to prepare a-1 until the positive active material of a-6.
(i-1)a-1
By Li 2cO 3and CoCO 3mix with given mol ratio, at 900 ℃, roasting is pulverized after 10 hours and classification, has obtained by chemical formula LiCoO 2the positive active material a-1 representing.
(i-2)a-2
Be the cobaltous sulfate that rises of 0.98mol/ to contain concentration be the aqueous solution of magnesium sulfate that 0.02mol/ rises by containing concentration, be supplied to continuously reactive tank, make the pH of solution reach 10～13 to dripping NaOH in reactive tank, the precursor of synthetic active substance, fully washes and makes it dry simultaneously.Consequently obtain with Co 0.98mg 0.02(OH) 2the hydroxide representing.This precursor and lithium carbonate are mixed, make the mol ratio of lithium and cobalt and magnesium reach 1: 0.98: 0.02, mixture pre-burning at 600 ℃ was pulverized after 10 hours.Then will, by the roasting 10 hours again at 900 ℃ of chippy calcining matter, pulverize and classification, obtained by chemical formula LiCo 0.98mg 0.02o 2the positive active material a-2 representing.
(i-3)a-3
Be that the nickelous sulfate that 0.82mol/ rises is also that the cobaltous sulfate that 0.15mol/ rises has carried out the aqueous solution of adjusting by concentration by containing concentration, be that the aluminum sulfate that 0.03mol/ rises is adjusted by concentration again, the aqueous solution after adjusting is supplied to reactive tank continuously, make the pH of solution reach 10～13 to dripping NaOH in reactive tank, the precursor of synthetic active substance, washes fully and makes it dry simultaneously.Consequently obtain with Ni 0.82co 0.15al 0.03(OH) 2the hydroxide representing.This precursor and lithium carbonate are mixed, make the mol ratio of lithium and nickel and cobalt and aluminium reach 1: 0.82: 0.15: 0.03, mixture is pulverized after 7 hours with 500 ℃ of pre-burnings under oxygen atmosphere.Then, will, by the roasting 15 hours again at 800 ℃ of chippy calcining matter, pulverize and classification, obtained by chemical formula LiNi 0.82co 0.15al 0.03o 2the positive active material a-3 representing.
(i-4)a-4
The aqueous solution that the nickelous sulfate of molar concentrations such as using, manganese sulfate and cobaltous sulfate have been adjusted is supplied to reactive tank continuously, make the pH of solution reach 10～13 to dripping NaOH in reactive tank, the precursor of synthetic active substance, washes fully and makes it dry simultaneously.Consequently obtain with Ni 1/3mn 1/3co 1/3(OH) 2the hydroxide representing.This precursor and lithium carbonate are mixed, make the mol ratio of lithium and nickel and manganese and cobalt reach 3: 1: 1: 1, mixture is pulverized after 7 hours with 500 ℃ of pre-burnings under oxygen atmosphere.Then will, by the roasting 15 hours again at 800 ℃ of chippy calcining matter, pulverize and classification, obtained by chemical formula LiNi 1/3mn 1/3co 1/3o 2the positive active material a-4 representing.
(i-5)a-5
Manganese dioxide and lithium carbonate is mixed, make the mol ratio of lithium and manganese reach 1: 2, by mixture under air ambient with 850 ℃ of roastings 10 hours, pulverize and classification, obtained by chemical formula LiMn 2o 4the positive active material a-5 representing.
(i-6)a-6
By lithium carbonate Li 2cO 3, ferric oxalate FeC 2o 42H 2o, ammonium dihydrogen phosphate (NH 4) 2hPO 4weighing, makes stoichiometric proportion reach 0.5: 1.0: 1.0 respectively, then fully mixes with mortar, at Ar-H 2under environment, with 600 ℃ of roastings 15 hours, obtain by chemical formula LiFePO 4the positive active material a-6 representing.
The thermal stability of the charged state to the positive active material a-1～a-6 preparing as mentioned above, evaluates as follows with DSC (RIGAKU TAS300).First, in the positive active material a-1～a-6 of 85 weight portions, mixed 10 weight portions are the PTFE as binding agent as the acetylene black of conductive agent and 5 weight portions, is shaped and is made into the electrode of sheet.This electrode is being used to the evaluation electricity consumption groove of Li metal to electrode for the work utmost point, to 0.2mA/cm 2constant current charge to the positive pole after 4.25V sample with appropriate amount, and be enclosed within the ware (pan) of fire-fighting SUS system.Programming rate with 10 ℃/min heats up.The temperature that starts the curve of DSC from baseline to rise starts temperature as heating.The heating obtaining under above condition starts temperature: a-1 is 202 ℃, and a-2 is 208 ℃, and a-3 is 215 ℃, and a-4 is 305 ℃, and a-5 is 320 ℃.Even if can not observing heating more than 400 ℃, a-6 starts.
(ii) making that anode mixture cream is stuck with paste
Use the positive active material a-1～a-6 obtaining with said method, made anode mixture cream shown below and stuck with paste.
(ii-1)a-11
Nmp solution, 90g that 3kg positive active material a-1,0.5kg are contained to the 12 % by weight PVDF (Wu Yu KCC system) as anodal binding agent stir as the acetylene black of conductive agent and appropriate NMP planetary-type mixer, have made anode mixture cream and have stuck with paste a-11.
(ii-2)a-21
Except positive active material a-1 is replaced with a-2, use with anode mixture cream and stick with paste the method that a-11 is identical, make anode mixture cream and stuck with paste a-21.
(ii-3)a-31
Except positive active material a-1 is replaced with a-3, use with anode mixture cream and stick with paste the method that a-11 is identical, make anode mixture cream and stuck with paste a-31.
(ii-4)a-41
Except positive active material a-1 is replaced with a-4, use with anode mixture cream and stick with paste the method that a-11 is identical, make anode mixture cream and stuck with paste a-41.
(ii-5)a-51
Except positive active material a-1 is replaced with a-5, use with anode mixture cream and stick with paste the method that a-11 is identical, make anode mixture cream and stuck with paste a-51.
(ii-6)a-61
Except positive active material a-1 being replaced with to the mixture that the weight ratio of positive active material a-3 and a-4 is 2: 1, use with anode mixture cream and stick with paste the method that a-11 is identical, make anode mixture cream and stuck with paste a-61.
(ii-7)a-71
Except positive active material a-1 being replaced with to the mixture that the weight ratio of positive active material a-3 and a-5 is 3: 1, use with anode mixture cream and stick with paste the method that a-11 is identical, make anode mixture cream and stuck with paste a-71.
(ii-8)a-81
Except positive active material a-1 is replaced with a-6, use with anode mixture cream and stick with paste the method that a-11 is identical, make anode mixture cream and stuck with paste a-81.
(iii) anodal making
The anode mixture cream obtaining in order to said method is stuck with paste a-11～a-81, has made positive pole shown below.
(iii-1)b-1
Be the two sides of the aluminium foil of 15 μ m at the thickness as anodal current collection base material, be first coated with anode mixture cream and stick with paste a-41 dry.Start to be from it coated with anode mixture cream and stick with paste a-11, dried film is rolled with roller, formed the anodal film being formed by 2 kinds of mixture layers.Thereafter, be 163 μ m by the THICKNESS CONTROL of the pole plate being formed by aluminium foil and anodal film, be made into positive plate b-1.The average thickness of the mixture layer of the top layer side that contains positive active material a-1 is counted 128 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-4 is counted 20 μ m (ratio of the average thickness average thickness outer field with it of the 1st mixture layer is 16: 100) take two sides.
(iii-2)b-2
Except the two sides at aluminium foil be first coated with anode mixture cream stick with paste a-41 and dry, be thereon coated with anode mixture cream stick with paste a-21 and dry, use the method identical with anodal b-1 to make anodal b-2.The average thickness of the mixture layer of the top layer side that contains positive active material a-2 is counted 125 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-4 is counted 20 μ m (ratio of the average thickness average thickness outer field with it of the 1st mixture layer is 16: 100) take two sides.
(iii-3)b-3
Except the two sides at aluminium foil be first coated with anode mixture cream stick with paste a-41 and dry, be thereon coated with anode mixture cream stick with paste a-31 and dry, use the method identical with anodal b-1 to make anodal b-3.The average thickness of the mixture layer of the top layer side that contains positive active material a-3 is counted 125 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-4 is counted 20 μ m with two sides.
(iii-4)b-4
Except the two sides at aluminium foil, be first coated with anode mixture cream stick with paste a-51 and dry, be thereon coated with anode mixture cream stick with paste a-31 and dry beyond, use the method identical with anodal b-1 to make anodal b-4.The average thickness of the mixture layer of the top layer side that contains positive active material a-3 is counted 130 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-5 is counted 15 μ m (ratio of the average thickness average thickness outer field with it of the 1st mixture layer is 12: 100) take two sides.
(iii-5)b-5
Except the two sides at aluminium foil be first coated with anode mixture cream stick with paste a-41 and dry, be thereon coated with anode mixture cream stick with paste a-61 and dry, use the method identical with anodal b-1 to make anodal b-5.The average thickness of the mixture layer of the top layer side of the mixture that contains positive active material a-3 and a-4 is counted 130 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-4 is counted 15 μ m with two sides.
(iii-6)b-6
Except the two sides at aluminium foil be first coated with anode mixture cream stick with paste a-51 and dry, be thereon coated with anode mixture cream stick with paste a-71 and dry, use the method identical with anodal b-1 to make anodal b-6.The average thickness of the mixture layer of the top layer side of the mixture that contains positive active material a-3 and a-5 is counted 130 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-5 is counted 15 μ m with two sides.
(iii-7)b-7
Except the two sides at aluminium foil be only coated with anode mixture cream stick with paste a-51 and dry, use the method identical with anodal b-1 to make anodal b-7.The average thickness of the mixture layer that contains positive active material a-5 is 140 μ m.
(iii-8)b-8
Except the two sides at aluminium foil be only coated with anode mixture cream stick with paste a-31 and dry, use the method identical with anodal b-1 to make anodal b-8.The average thickness of the mixture layer that contains positive active material a-3 is 145 μ m.
(iii-9)b-9
Except the two sides at aluminium foil be first coated with anode mixture cream stick with paste a-31 and dry, be thereon coated with anode mixture cream stick with paste a-51 and dry, use the method identical with anodal b-1 to make anodal b-9.The average thickness of the mixture layer of the top layer side that contains positive active material a-5 is counted 15 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-3 is counted 130 μ m with two sides.
(iii-10)b-10
Except the two sides at aluminium foil be first coated with anode mixture cream stick with paste a-81 and dry, be thereon coated with anode mixture cream stick with paste a-31 and dry, use the method identical with anodal b-1 to make anodal b-10.The average thickness of the mixture layer of the top layer side that contains positive active material a-3 is counted 140 μ m with two sides, and the average thickness of the mixture layer of the current collection base material side that contains positive active material a-6 is counted 10 μ m (ratio of the average thickness average thickness outer field with it of the 1st mixture layer is 7: 100) take two sides.
(iii-11)b-11
Stick with paste in a-41 at anode mixture cream, in 1 minute, successively adding on a small quantity the anode mixture cream of same amount sticks with paste a-31 and stirs, simultaneously by the blending ratio obtaining in the process of interpolation gradually different anode mixture cream stick with paste, be coated on successively the two sides of aluminium foil, be then dried.In addition utilize the method identical with anodal b-1 to make following anodal b-11, the starting towards the thickness direction of current collection base material side from top layer side of anodal film, the content of positive active material a-4 increases (content of positive active material a-3 reduces continuously) continuously.The average thickness of anodal film is counted 150 μ m with two sides.
(iv) making of negative pole
(iv-1)c-1
Delanium using 3kg as negative electrode active material, 75g are as " BM-400B " (trade name of negative pole binding agent, ZEON Co., Ltd. of Japan system, the aqueous liquid dispersion of the modification body that contains 40 % by weight styrene-butadiene copolymer), 30g stirs as the carboxymethyl cellulose (CMC) of thickener and appropriate water planetary-type mixer, is prepared into cathode agent coating.The negative pole current collection base material that this coating is coated on except negative wire connecting portion is that thickness is the two sides of the Copper Foil of 10 μ m, and dried film is rolled with roller, makes negative plate.Now, by the THICKNESS CONTROL of the pole plate being formed by Copper Foil and anode mixture layer be 180 μ m.
(iv-2)c-2
Si (purity 99.999%, Furuuchi Chemical Corporation system, ingot) is put into graphite-made crucible.By the electrolysis Cu paper tinsel of making current collection substrate sheet, (thickness 18 μ m) attach and are fixed on the water cooled rolls being arranged in vacuum deposition apparatus for FurukawaCircuit Foil Co., Ltd. system.The graphite-made crucible that has added Si being set under it, the nozzle that imports oxygen is set between crucible and Cu paper tinsel, is that 20sccm (flows through 20cm in 1 minute by the flow control of oxygen (Nippon Sanso Corp's system, purity 99.7%) 3flow), in vacuum deposition apparatus, import oxygen.Use electron gun to carry out vacuum evaporation.Evaporation condition is made as: accelerating voltage is-8kV that electric current is 500mA.
The thickness of the film that contains active material of each one side of negative pole is about 18 μ m.In addition, measure oxygen containing amount in this negative pole by combustion method, distinguished it is by SiO 0.3the composition representing.
(v) preparation of nonaqueous electrolyte
Containing in the mixture of nonaqueous solvents that volume ratio is ethylene carbonate (EC), dimethyl carbonate (DMC) and the methyl ethyl carbonate (EMC) of 2: 3: 3, the LiPF that concentration of ordinary dissolution is 1mol/L 6, make nonaqueous electrolyte.
(vi) making of cylindrical battery
First, by ultrasonic bonding, positive wire made of aluminum is arranged on positive pole.Similarly the negative wire being made of copper is arranged on negative pole.Thereafter, between both positive and negative polarity, folder, across the micro-porous polyethylene of the band shape wider than two-plate barrier film processed, is wound into cylindric and formation pole plate group.The configuring respectively up and down the dead ring of polypropylene system and insert in battery case of pole plate group, form after end difference on the top of battery case, inject above-mentioned electrolyte, be the cylindrical battery that 18mm, height overall are 65mm thereby be made into diameter with hush panel sealing.
In negative pole, use the battery of c-1 respectively as embodiment 1～7 using used b-1～b-6 and b-10 in positive pole, in negative pole, use the battery of c-2 respectively as embodiment 8 and 9 using used b-3 and b-10 in positive pole, in negative pole, used the battery of c-1 as embodiment 10 using used b-11 in positive pole.In addition, b-7～b-9 will have been used in positive pole and the battery that used c-1 in negative pole respectively as a comparative example 1～3.
Carrying out after given discharging and recharging, these batteries have been carried out to following evaluation.
(battery capacity measuring)
Each battery is discharged and recharged under the following conditions.Discharge capacity is illustrated in table 1.
Constant current charge: 1680mA, final voltage 4.2V
Constant voltage charging: stop electric current 240mA, time out 30 minutes
Constant current discharge: electric current 480mA, final voltage 3.0V, time out 30 minutes
(pin prick test condition)
To the battery after solid measure, under the condition identical with this solid measure, to charge, nail made of iron (diameter is as 1.9mm) is run through battery by the speed take 5mm/s in the temperature groove under 20 ℃ of environment.Monitor cell voltage now, measure because nail makes battery short circuit start the cell voltage after 1 second and the minimum of the cell voltage that observed during this period.The cell voltage of each battery before just short circuit is 4.17V.
The results are shown in table 1.
[table 1]
Battery Positive plate Negative plate Battery capacity (mAh) Cell voltage minimum (V) Cell voltage (V) after 1 second
Embodiment 1 b-1 c-1 2445 3.46 3.99
Embodiment 2 b-2 c-1 2430 3.50 4.07
Embodiment 3 b-3 c-1 2780 3.66 4.02
Embodiment 4 b-4 c-1 2735 3.68 4.03
Embodiment 5 b-5 c-1 2645 3.76 4.11
Embodiment 6 b-6 c-1 2585 3.77 4.08
Embodiment 7 b-10 c-1 2695 3.86 4.13
Embodiment 8 b-3 c-2 3025 3.79 4.14
Embodiment 9 b-10 c-2 3010 3.93 4.16
Embodiment 10 b-11 c-1 2765 3.70 4.01
Comparative example 1 b-7 c-1 1980 3.95 4.09
Comparative example 2 b-8 c-1 2700 0.25 0.25
Comparative example 3 b-9 c-1 2210 0.56 0.56
The positive electrode for lithium secondary battery of embodiment 1～4 and 7～9, on aluminium foil, form respectively 2 laminated doses of layers, each layer contains respectively a kind of heating and starts temperature different lithium-containing compound, with the 1st nearest mixture layer of aluminium foil in, containing heating and starting the lithium-containing compound of temperature more than 300 ℃.Specifically, in the 1st mixture layer, embodiment 1～3 and 8 contains lithium-nickel-manganese-cobalt oxide, and embodiment 4 contains lithium manganese oxide, and embodiment 7 and 9 contains olivine-type lithium phosphate compound.
In the positive electrode for lithium secondary battery of embodiment 5,6 and 10, starting towards the thickness direction of current collection base material side from top layer side of anodal film, heating starts the lithium-containing compound of temperature more than 300 ℃ to be increased.Specifically, in embodiment 5, the containing ratio of lithium-nickel-manganese-cobalt oxide is periodically increased to 100% from 33%, in embodiment 6, the containing ratio of lithium manganese oxide is periodically increased in 100%, embodiment 10 from 25%, and the containing ratio of lithium-nickel-manganese-cobalt oxide increases continuously.
Compared with the comparative example 2 that only contains the lithium nickel oxide that heating beginning temperature is low with mixture layer, these embodiment, in pin prick test, can confirm to have the excellent results that suppresses the cell voltage reduction being caused by short circuit.
Start in the lithium-containing compound of temperature in the heating having more than 300 ℃, especially olivine-type lithium phosphate compound is identified the effect (embodiment 7 and 9) of good inhibition lower voltage.
In pin prick test, the effect of higher inhibition lower voltage represents, contain heating and start the lithium-containing compound of temperature more than 300 ℃ by making the 1st mixture layer nearest with anodal current collection base material or being coated with membrane portions with the nearest positive pole of current collection base material, even the in the situation that of having produced high Joule heat because of short circuit in the time of pin prick test, also can conscientiously suppress the overheated of lithium secondary battery.
In addition, in comparative example 3, the 1st mixture layer nearest with aluminium foil contains the lithium nickel oxide that heating beginning temperature is low, and the skin of the 1st mixture layer contains heating and starts the high lithium manganese oxide of temperature.Although comparative example 3 is that in embodiment 4,2 laminated doses of contained lithium-containing compounds of layer have carried out the form of exchanging in form, but after exchanging like this, in pin prick test, substantially do not see the effect that suppresses lower voltage, clearly the reliability in the time of pin prick test is lower.
And, compared with comparative example 2 and 3, the reduction of the cell voltage that the lithium-containing compound in the formation of embodiment 1～10 not only can suppress to be caused by short circuit, but also confirm to have the effect of the voltage (voltage after 1 second) that minimum voltage (cell voltage minimum) while returning to than short circuit is higher.That is to say, contain heating and start the lithium-containing compound of temperature 300 ℃ or more by making the 1st mixture layer nearest with anodal current collection base material or being coated with membrane portions with the nearest positive pole of current collection base material, the potential difference between the voltage when minimum voltage can utilize short circuit time and recovery is controlled and is discharged and recharged.
On the other hand, only formed in anodal comparative example 1 by the lithium manganese oxide of beginning temperature more than 300 ℃ that generate heat, although demonstrated the effect of higher inhibition lower voltage in pin prick test, because the capacity density of lithium manganese oxide is low, therefore battery capacity reduces.
As described above, one aspect of the present invention is a kind of positive electrode for lithium secondary battery as described below: comprise current collection base material and on described current collection base material, have the anodal film of multiple mixture layers; Wherein, described anodal film, contains the lithium-containing compound that starts different two or more of temperature as the heating of positive active material; In described two or more lithium-containing compound, at least a kind of lithium-containing compound has 300 ℃ of above heatings and starts temperature; The 1st mixture layer nearest with described current collection base material, contains at least a kind of described heating and starts the lithium-containing compound of temperature more than 300 ℃.According to described formation, by with pin prick test in produce due to internal short-circuit in the 1st nearest mixture layer of the current collection base material of high Joule heat, contain at least a kind of heating and start the lithium-containing compound of temperature more than 300 ℃, the positive pole that just can conscientiously suppress to be caused by internal short-circuit generates heat, and anodal thermal runaway is limited in to Min..In addition, anodal film of the present invention is owing to can containing other lithium-containing compounds except heating starts the lithium-containing compound of temperature 300 ℃ or more, generating heat that beginning temperature is low but therefore other lithium-containing compounds that capacity density is large can realize high power capacity as anodal entirety.Consequently can provide that conscientiously to suppress the battery of pin prick test overheated and be the positive electrode for lithium secondary battery of high power capacity.
In addition, the positive active material of the 1st mixture layer starts, the lithium-containing compound of temperature more than 300 ℃, can also contain except other lithium-containing compounds it except containing heating.In this case, the content that heating starts the lithium-containing compound of temperature more than 300 ℃ is preferably more than the content except other lithium-containing compounds it.According to described formation, the positive pole that just can conscientiously suppress to be caused by internal short-circuit generates heat, and can realize high power capacity simultaneously.
And, in the 1st mixture layer, preferably in fact only contain heating as positive active material and start the lithium-containing compound of temperature more than 300 ℃.By in because of pin prick test because internal short-circuit produces in the 1st mixture layer of high Joule heat, only contain heating and start the lithium-containing compound of temperature more than 300 ℃, thickness that can attenuate the 1st mixture layer, can further suppress the positive pole heating causing due to internal short-circuit simultaneously conscientiously.
Another aspect of the present invention is positive electrode for lithium secondary battery as described below: comprise current collection base material and the anodal film on described current collection base material; Wherein, described anodal film, contains the lithium-containing compound that starts different two or more of temperature as the heating of positive active material; In described two or more lithium-containing compound, at least a kind of lithium-containing compound has 300 ℃ of above heatings and starts temperature; On the top layer of described anodal film, to the thickness direction of current collection base material, described heating starts the content of the lithium-containing compound of temperature more than 300 ℃, increases towards current collection base material side from top layer side.According to described formation, by with pin prick test in be coated with membrane portions because internal short-circuit produces the nearest positive pole of the current collection base material of high Joule heat, the amount that contains the lithium-containing compound of heating beginning temperature more than 300 ℃ is for maximum, just can conscientiously suppress the positive pole heating causing due to internal short-circuit, anodal thermal runaway is limited in to Min..Simultaneously, due to can be on the thickness direction from top layer to current collection base material of anodal film, make other lithium-containing compounds except heating starts the lithium-containing compound of temperature 300 ℃ or more, the i.e. low but content of other lithium-containing compounds that capacity density is large of beginning temperature that generates heat, increase towards current collection base material side from top layer side, therefore can suppress the positive pole heating causing due to internal short-circuit, realize high power capacity simultaneously.Consequently can provide the battery that can conscientiously suppress in pin prick test overheated and be the positive electrode for lithium secondary battery of high power capacity.
In addition, being coated with in membrane portions with the nearest positive pole of current collection base material, preferably in fact only contain the lithium-containing compound of heating beginning temperature more than 300 ℃ as positive active material.By with pin prick test in be coated with membrane portions because internal short-circuit produces the nearest positive pole of the current collection base material of high Joule heat, only contain heating and start the lithium-containing compound of temperature more than 300 ℃, just can further conscientiously suppress the positive pole heating causing due to internal short-circuit, and conscientiously guarantee high power capacity.
Of the present invention is again the lithium secondary battery that has possessed above-mentioned positive electrode for lithium secondary battery and negative pole and nonaqueous electrolyte on the other hand.The positive electrode for lithium secondary battery of the application of the invention, just can obtain the lithium secondary battery that in pin prick test, reliability is good and capacity is high.
Positive electrode for lithium secondary battery of the present invention can suppress the overheated of lithium secondary battery in pin prick test conscientiously.Therefore,, by using described positive electrode for lithium secondary battery, can be provided in the lithium secondary battery that in pin prick test, reliability is good and capacity is high.Lithium secondary battery of the present invention can be in portable data assistance, portable electric appts, domestic small electrical storage device, motorcycle, electric automobile, hybrid electric automobile etc.

Claims (19)

1. a positive electrode for lithium secondary battery, comprises current collection base material and on described current collection base material, has the anodal film of multiple mixture layers;
Described anodal film contains the lithium-containing compound that starts different two or more of temperature as the heating of positive active material;
In described two or more lithium-containing compound, at least a kind of lithium-containing compound has 300 ℃ of above heatings and starts temperature;
With in the 1st nearest mixture layer of described current collection base material, contain at least a kind of described heating and start the lithium-containing compound of temperature more than 300 ℃,
It is characterized in that,
It is by Li that the heating of described at least a kind starts the lithium-containing compound of temperature more than 300 ℃ ani 1-(b+c)mn bco co 2the lithium-nickel-manganese-cobalt oxide representing, in aforementioned formula, 1≤a≤1.2,0.1≤b≤0.5,0.1≤c≤0.5.
2. positive electrode for lithium secondary battery according to claim 1, it is characterized in that, in the positive active material of described the 1st mixture layer, described heating starts the content of the lithium-containing compound of temperature more than 300 ℃ more than the content except other lithium-containing compounds it.
3. positive electrode for lithium secondary battery according to claim 1, is characterized in that, as the positive active material in described the 1st mixture layer, only contains described heating and starts the lithium-containing compound of temperature more than 300 ℃.
4. positive electrode for lithium secondary battery according to claim 1, is characterized in that, described heating starts the lithium-containing compound of temperature more than 300 ℃ and further comprises at least a kind that is selected from lithium manganese oxide, olivine-type lithium phosphate compound.
5. positive electrode for lithium secondary battery according to claim 4, is characterized in that, described lithium manganese oxide is by LiMn 2o 4the lithium manganese oxide representing.
6. positive electrode for lithium secondary battery according to claim 4, is characterized in that, described olivine-type lithium phosphate compound is by LiMePO 4the olivine-type lithium phosphate compound representing, in aforementioned formula, Me is at least a kind that is selected from Co, Ni, Fe and Mn.
7. positive electrode for lithium secondary battery according to claim 1, is characterized in that, other lithium-containing compounds except described heating starts the lithium-containing compound of temperature more than 300 ℃ are at least a kind that is selected from lithium and cobalt oxides and lithium nickel oxide.
8. positive electrode for lithium secondary battery according to claim 7, is characterized in that, described lithium and cobalt oxides is by LiCoO 2or Li aco 1-(b+c)mg bm co 2the lithium and cobalt oxides representing, in aforementioned formula, 1≤a≤1.05,0.005≤b≤0.10,0.005≤c≤0.10, M is at least a kind that is selected from Al, Sr and Ca.
9. positive electrode for lithium secondary battery according to claim 7, is characterized in that, described lithium nickel oxide is by Li ani 1-(b+c)co bm co 2the lithium nickel oxide representing, in aforementioned formula, 1≤a≤1.05,0.1≤b≤0.35,0.005≤c≤0.30, M is at least a kind that is selected from Al, Sr and Ca.
10. a lithium secondary battery, is characterized in that, possesses positive electrode for lithium secondary battery claimed in claim 1, negative pole and nonaqueous electrolyte.
11. 1 kinds of positive electrode for lithium secondary batterys, comprise current collection base material and the anodal film on described current collection base material;
Described anodal film contains the lithium-containing compound that starts different two or more of temperature as the heating of positive active material;
In described two or more lithium-containing compound, at least a kind of lithium-containing compound has 300 ℃ of above heatings and starts temperature;
It is characterized in that,
It is a kind that is selected from lithium manganese oxide, lithium nickel cobalt manganese oxide and olivine-type lithium phosphate compound that described heating starts the lithium-containing compound of temperature more than 300 ℃;
On the top layer of described anodal film, to the thickness direction of current collection base material, the content that described heating starts the lithium-containing compound of temperature more than 300 ℃ is and periodically increases or increase continuously with 3 layers towards current collection base material side from top layer side.
12. positive electrode for lithium secondary batterys according to claim 11, is characterized in that, are coated with and in membrane portions, only contain described heating as positive active material and start the lithium-containing compound of temperature more than 300 ℃ with the nearest positive pole of described current collection base material.
13. positive electrode for lithium secondary batterys according to claim 11, is characterized in that, described lithium manganese oxide is by LiMn 2o 4the lithium manganese oxide representing.
14. positive electrode for lithium secondary batterys according to claim 11, is characterized in that, described lithium nickel cobalt manganese oxide is by Li ani 1-(b+c)mn bco co 2the lithium-nickel-manganese-cobalt oxide representing, in aforementioned formula, 1≤a≤1.2,0.1≤b≤0.5,0.1≤c≤0.5.
15. positive electrode for lithium secondary batterys according to claim 11, is characterized in that, described olivine-type lithium phosphate compound is by LiMePO 4the olivine-type lithium phosphate compound representing, in aforementioned formula, Me is at least a kind that is selected from Co, Ni, Fe and Mn.
16. positive electrode for lithium secondary batterys according to claim 11, is characterized in that, other lithium-containing compounds except described heating starts the lithium-containing compound of temperature more than 300 ℃ are at least a kind that is selected from lithium and cobalt oxides and lithium nickel oxide.
17. positive electrode for lithium secondary batterys according to claim 16, is characterized in that, described lithium and cobalt oxides is by LiCoO 2or Li aco 1-(b+c)mg bm co 2the lithium and cobalt oxides representing, in aforementioned formula, 1≤a≤1.05,0.005≤b≤0.10,0.005≤c≤0.10, M is at least a kind that is selected from Al, Sr and Ca.
18. positive electrode for lithium secondary batterys according to claim 16, is characterized in that, described lithium nickel oxide is by Li ani 1-(b+c)co bm co 2the lithium nickel oxide representing, in aforementioned formula, 1≤a≤1.05,0.1≤b≤0.35,0.005≤c≤0.30, M is at least a kind that is selected from Al, Sr and Ca.
19. 1 kinds of lithium secondary batteries, is characterized in that, possess positive electrode for lithium secondary battery, negative pole and nonaqueous electrolyte described in claim 11.
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